Circulating fan



Oct. 6, 1936. v. WEBER 2,056,547

CIRCULATING FAN Filed Sept. 1, 1954 3 Sheets-Sheet 1 Filed Sept. 1, 1954 v. WEBER 2,056,547

Oct. 6, 1936. v. WEBER 2,056,547

' CIRCULATING FAN Filed Sept. 1, 1934 3 Sheets-Sheet 5 Patented Oct. 6, 1936 UNITED STATES OIRCULATING FAN Victor Weber, St. Louis, Mo., asslgnor to The Emerson Electric Mfg. 00., St. Louis, Mo., a corporation of Missouri Application September 1, 1934, Serial No. 741,645

19 Claims. (6!. -159) This invention relates to circulating fans and particularly to the impeller itself.

An object of the invention is to provide a fan which will be nearly noiseless in operation, which will have high efilciency, which will lend itself to a pleasing design, which will be economical of construction, and which will be durable in operation.

Other and specific objects will be apparent from the following detail description, taken in connection with the accompanying drawings, in

which- Fig. 1 is a front elevation of a complete circulating fan embodying the invention;

Fig. 2 is a vertical section'of the structure illustrated in Fig. 1; and

Figs. 3, 4, and 5 are diagrams showing the arrangement of the fan blades on the hub, one blade only being shown attached to a hub cup, which is in turn secured to a propelling shaft; Fig. 3 being a plan view, Fig. 4 a front elevation, and Fig. 5 a side elevation.

As shown in Fig. 1 the fan, when viewed from the front, presents substantially a closed circle with the trailing edge of a blade somewhat overlapping the leading edge of the adjacent blades. In the construction specifically shown in the drawings four blades are used, although it will be obvious that a more or less number may be employed. However that may be, the area of each blade will beat least nearly equal to the total area traversed divided by the number of blades, such area being sometimes termed herein, fan disc.

The invention contemplates the use of a convex hub cup which may be hemispherical in form, or conical in form, or a variation of the two, attached at its apex to a driving shaft with the blades secured to the outer periphery of the cup and with a substantial portion of the inner edge of the blade conforming to the surface of the cup. Or, otherwisedescribed, the cup includes a forward surface which converges forwardly'and inwardly with reference to its axis.

The blades when attached to the cup are in the form of a uniformly developed helix, with a constant pitch, with the effective or front surface of the blade coinciding with lines which are radial from and perpendicular to the axis of revolution.

As best shown in Fig. 4, a blade may be considered as divided into two parts almost equal in extent, a leading end and a trailing end, the leading end being free and extending rearwardly from the cup and the trailing end having an inner edge secured to and adjacent the periphery of the cup.

The arrangement is such that a cylindrical air stream is developed having a uniform velocity throughout the cylinder with a constant and uniform thrust being applied to the air stream. This function results in an increased efliciency in a 5 fan because of the avoidance of circumferential currents and eddy currents, and also results in quietness of operation.

It is thought that in the fan employed, the air stream is accelerated materially and to a greater 10 extent than in conventional fan structures by the vacuum produced at the rear of the fan. On this account and because there is a uniform thrustthroughout the surface of the blade with no particular part performing an increased duty 15 I over other parts, vibration and noise are reduced to a minimum. I

The invention has now been described generally and its essential characteristics are pointed out in the appended claims, but a more detailed description of the specific device illustrated in the drawings is now attempted to assist in understanding and practicing the invention.

The mounting of the fan may be generally described because it is particularly adapted to this 25 specific purpose, although it is no part of this invention and is more particularly illustrated and described in a copending application by my collaborator, Herbert I. Finch, Serial No. 699,499, filed November 24, 1933 The mounting of the fan includes a-base I,

to which is attached a plate 2, which is adjustable with reference to the base I and which is adapted to oscillate by appropriate mechanism including support, which has a plurality. of circular members 1 and a plurality of transverse members 8 fabricated together in open pattern work. Two

of the members 1 are securely clamped to the plate 2 as shown at 9, and the unitary guard and 45 support is thereby secured in upstanding fashion with reference to the plate 2 and with reference to the base I.

The motor and fan, which is attached to the motor shaft, is supported within and by the 50 guard by a plurality of radialstraps I0 which have their outer ends clamped to the guard, to one of the circular members as specifically shown,v and their inner ends secured directly or indirectly to the motor frame. In the structure as specifi- 66' cally shown the inner end of the straps It are secured by screws ii to a cup I2 which is attached by screws it at the rear of the motor frame.

The resuit of this particular construction is that the motor and impeller are supported within the guard by the guard itself, and, since the guard is fabricated of resilient members, the motor and impeller are thus resiliently supported so as to reduce the amount of vibration transmitted irom the motor and impeller to the base. Furthermore, since the fan blades overhang a substantial part of the motor frame, as will be understood from the following description, the ordinary con ventional mounting is not suitable and the mounting which has been illustrated and just described permits the motor and impeller to be supported from the rear end of the motor frame and to the rear of the fan blades.

The fan or impeller includes a plurality of blades which are attached to a hub cup I4, which is secured to the shaft 65 by a sleeve member I5.

In the specific construction as shown, the member I5 is internally threaded to engage a threaded end of the shaft 6. The member l5 has a rounded circular head which carries a circumferential outer flange lii'and an inner flange Il, as shown in Fig. 2, between which flanges the apex of the cup I l is secured, the cup I4 having a suitable circular hole It for this purpose.

The exact geometrical form of the cup i4 is not important, it being essential only that it be concave or converge toward the front, for instance, as a hemisphere or cone. In the device asspeciiically illustrated in the drawings, the cup Iii includesa rim l9, which is a cylinder, 2. portion 20 on one degree of curvature and a portion M on a different degree of curvature. Theportion I9 extends from the rear of the cup, as shown in Fig. 3, to a line 0A, the portion 26 extends from the line 0A 22 to a line OB, and the portion 2i extends from the line 03 to the margin of the hole l8. Although the exact dimensions and exact curvature are not essential, for the purpose of ready understanding of the drawings and of the invention and to permit its ready application, typical dimensions and curvatures, as specifically illustrated in the drawings, will be given. The cup I4 has an external diameter at the portion I9 of 4 and that portion extends axially for a distance of 9/32". The portion 20 is a spherical section on the same radius as the cup, that is 2", and extends from the line On. to the line OB, a distance of 22 The portion 26 extends from the line OB to the margin of the hole it; and is on a radius of 2%".

It will thus be seen that the cup it may be considered either as a modified hemisphere or as a modified cone, but it is to be understood that further modifications of either would be entirely suitable as an embodiment of the invention. The entire axial length of the cup, exclusive of the member I5, is 2 /2".

As previously explained, the fan blade is arranged along the path of a uniformly developed helix and the surface of the fan blade constitutes, or coincides with, a plurality of radial lines extending from and perpendicular to the axis. An explanation of the contour of the blade can best be made by reference to a number of such radial lines shown in Fig. 4.

The point 0 is any appropriate point in the axis of revolution. The line 0-0 is the line dividing the blade into two parts, a leading end 22 and a trailing end 23. The line 00 intersects the lead .mensions or curvatures.

absence ing end and is approximately 30 from the line 0-0. The line OD is tangent to the leading extremity and is 49 from the line M. The line OE intersects the trailing edge and is approximately 20 from the line O-O. The line 0? touches the trailing tip and is from the line 0-4).

With the use of the radial lines just described a description of the contour of the blade may be more easily made. A part 25 of the outer contour or edge oi the blade from the point C to the E, a distance of approximately 50", is the cir= cuinierence or" the disc oi the fan. Taking the actual exemplification, this may be a radius cf; 57!. from the point C to the point D, is on a much less radius, for example 1 The part 25 of the inner edge from the point D to the point approximately 0" is on a radius of 3%", following the example given. That part 21 of the outer edge on the trailing end of the fan, extending from the point E to the point F, a distance of approximately 65", is on a radius of 2&5". The inner edge 28 of the fan extending from the trailing tip F to the point 0'' is cut to fit the cup member I4 when the fan blade is attached, as explained, that is along a uniform helix.

It will be observed, therefore, that the outer edge of the blade is convex from the leading extremity to the trailing tip, including a substantial part in both the leading end and the trailing end, that Is the same curvature as the circumi' r= ence of thefan disc. The irmer edge from the leading extremity to the trailing tip extends continuously forwardly and inwardly with reference to the axis oi revolution throughout its entire length. Of the inner edge one part, which is approximately that adjacent the leading end, is convex, and the other part, which is adjacent the trailing end, is concave and contacts, or follows, the contour of the hub cup.

The helix in the example given is on a 9" pitch. That is to say, for each 10 the blade advances one quarter inch in an axial direction. Thus, the trailing tip F, being 85 in advance of the line OO is 2 forwardly of that line. The leading edge D, being 49 rearwardly from the line 0-0, is 1%" (almost) behind that line, and the blade extends, therefore, a distance of 3%" (almost) axially from the leading edge to the trailing tip.

The fan is attached to the cup it by means of a flange 29, integral with the fan blade, which is secured to the cup I4 by rivets 30. A lug M which fits in an appropriate socket in the cup M serves to hold the trailing tip in position and prevents its vibration.

It will be understood that where specific dimensions and specific degrees of curvature are mentioned they are mentioned only for the purpose of exemplification and explanation, and the invention is not to be limited to any precise di- These dimensions, of course, must be varied for different sizes of propellers, and the dimensions and curvatures will be varied where the number of fan blades employed differ from that shown in the specific embodiment. Furthermore, the structure may be varied in some respects and degrees without materially changing the result, and otherwise to secure additional or modified results. Such modifications, within the scope of the appended claims, are contemplated and are within the spirit of this invention.

The part 25 on the leading edge, extending 2,066,547 verging inwardly and forwardly with reference- I claim:

1. In a fan, a plurality of blades, each lying along a uniformly developed helix about the axis of rotation and having its effective surface formed on radial lines extending from and perpendicular to the axis of rotation, the combined area of the blades being at least equal to the disc area of the fan.

2. A fan blade having a leading extremity a substantial distance from the axis of rotation and a trailing tip close to said axis, and an inner edge extending forwardly with respect to the front of the fan and inwardly with reference to its axis of rotation from its leading extremity to its trailing tip, having an arcuate dimension measured in a plane perpendicular to its axis at least greater than 90.

3. In a fan, a plurality of blades having a leading extremity a substantial distance from the axis of rotation, and a trailing tip close to said axis, and each having a convex outer edge extending from its leading extremity to its trailing tip and having an inner edge extending forwardly with respect to the front of the fan and inwardly with reference to its axis of rotation from the leading extremity to the trailing tip, the combined area of the blades being at least equal to the disc area of the fan.

4. A fan blade of a configuration lying along a helix about its normal axis of rotation having a leading end and a trailing end with the inner edge of the trailing end extending continuously forwardly with respect to the front of the fan and inwardly with reference to its axis of rotation, having its outer edge convex from its leading extremity to its trailing tip.

5. A fan blade having a leading end and a trailing end with the inner edge of the leading end convex and the inner edge of the trailing end concave to extend from the leading extremity forwardly with respect to the front of the fan and inwardly with reference to the axis of rotation, the convex portion and the concave portion meeting and extending from the leading extremity of the blade to the trailing tip.

6. A fan blade having a leading end and a trailing end with the inner'edge of the leading end convex and the inner edge of the trailing end con cave to extend from the leading extremity forwardly with respect to the front of the fan and inwardly with reference to the axis of rotation, the convex portion and the concave portion meeting and extending from the leadingextremity of the blade to the trailing tip, and having an outer edge convex from the leading extremity to the trailing tip.

7. In a fan, a hub cup having a convex surface converging forwardly, and a plurality of fan blades attached to the cup, each having its trailing end contiguous to the convex surface for a substantial distance, extending forwardly and inwardly along said surface with reference to the axis of rotation, and having its leading end free and extending rearwardly from the rear edge of the cup.

8. In a fan, a hub cup having a surface converging inwardly and forwardly from its rim with reference to the axis of rotation, and a plurality of blades attached to said cup, each lying along a uniformly developed helix and having an inner edge contiguous to said surface for a substantial distance, and terminating close to the axis of rotation.

9. In a fan, a hub cup having a surface conto the axis of rotation, and a plurality of blades attached to said cup, each having a leading end and a trailing end with the inner edge of the trailing end contiguous to said converging surface and its leading end extending rearwardly beyond said cup over a substantial portion of the motor frame.

10. In a fan, a hub cup having a surface converging inwardly and forwardly with reference to the axis of rotation, and a plurality of blades attached to said cup, each having a leading end and a trailing end with the inner edge of the leading end convex and the inner edge of the trailing end concave and in conformity with the surface of the cup to which it is contiguous, the

convex portion and the concave portion meeting and extending from the leading extremity of the blade to the trailing tip, the combined area of the blades being at least equal to the disc area of the fan.

11. In a fan, a hub cup having a surface converging inwardly and forwardly with reference to the axis of rotation, and a plurality of blades attached to said cup, each lying along a uniformly developed helix and each having a trailing end with a concave inner edge contiguous to said converging surface for a substantial distance, the combined area of the fan blades being at least equal to the fan disc.

12. In a fan, a hub cup having a surface converging inwardly and forwardly with reference to the axis of rotation, and a plurality of blades attached to said cup, each having a trailing end with a concave inner edge contiguous to said converging surface for a substantial distance adjacent the trailing edge, lying along a uniformly developed helix, and having its effective surface coinciding with lines radial from and perpendicular to the axis of rotation, the combined area of the fan blades being at least equal to the disc' area of the fan.

13. In a device of the kind described, a motor,

. motor, and the extremity thereof projecting be yond the hub element and over the motor.

-15. In a fan, a motor, a hub extending over said motor, a helical blade on said hub, said blade having a leading end projecting from said hub back over the motor, and a trailing edge extending forwardly along the hub.

16. A fan impeller including a hub and a blade, the blade extending rearwardly and outwardly from said hub to a leading point, thence forwardly and outwardly from said leading point to a given point, whereby to define a leading end of substantial peripheral extent having a convex leading edge, and the trailing end being formed of a spiral originating approximately at the axis and extending out to the maximum radial dimension of the blade.

17. A fan including a hub, four blades mounted on said hub, said blades each lying along a helix about the axis oi. rotation of the hub, and the combined area of the blades being substantially equal to the disc area of the fan.

18. A fan including a hub having a surface converging toward the axis of rotation, four helicoidal blades on said hub, the' combined area of the blades being substantially equal to the disc area of the Ian, andone end of each blade following the contour oi the hub and terminating close to the axis oi rotation.

19. In a fan, a plurality of blades, each lying along a helix about the axis of rotation and having its eflective surtace formed on radial lines extending from the axis of rotation, the combined area of the blades being 'at least equal to the disc area of the fan.

VICTOR WEBER. 

